Luminair



Aug. 13, 1929. O PH 1,724,726

'LUMINAIR Original Filed Dec. 1927 INVENTOR ATTORNEY Patented Aug. 13,1929.

UNITED STATES 1,724,726 PATENT OFFICE.

THOMAS W. ROLPH, OF NEWARK,.OHIO, ASSIG IOR TO HOLOPI-IANE COMPANY,INC.,

OF YORK, N. Y., A CORPORATION OF NEXV YORK.

LUMINAIR.

Application filed December 2, 1927, Serial This invention relates toimprovements in luminaires for general interior illumination andparticularly luminaires for direct lighting as employed in class rooms,offices, and other places where light on the working plane is desired.In such lighting equipment it is desirable to have a large part of thelight distributed in various desirable ways within the 0-60 zone, 0being measured directly downward or at the nadir and being 30 below thehorizontal. This light in the 0-60 zone is the light which contributesvery largely to the direct illumination of the lower part of the room,where the highest illumination is usually required.

It is also desirable in such luininaires to have the amount of light inthe zone 60-90 (90 being the horizontal) small. lVhile this zonecontributes something to the direct illumination it contributes muchmore to the unnecessary. illumination of walls; furthermore, the lightin this zone is the light which is most apt to interfere with visionbecause it strikes the eyes of the occupants of the room, directly fromthe luminair, at angles most nearly approaching the customary lines ofvision.

Above the horizontal the light may be of a higher intensity than betweenGO 0 but considerations of efficiency dictate that it should be of lowerintensity than the direct light in the 060 zone.

In order to meet the requirements set forth above with efliciency in theutilization of light, I have devised a luminair of unique construction.

The figure is an elevation bisected to show the construction in crosssection. In the figure, 1 is a light source, here taken as a modernelectric lamp, which lamp is surrounded by a cup 2, having a prismaticconstruction preferably, but not essentially, on its outer surface. Thecup is held in place by a spring 11, which presses against the lowerplate or bowl 4. The bowl is fastened by means of clips 12 to an upperreflecting part 3. 13 indicates a holding ring which is adapted to befastened to any sort of suspension or ceiling holder. The upper edge ofthe cup is in contact with a ledge on the reflector at 14. The innersurface of reflector 3 and bowl 4 are provided with a definite prismaticconstruction as hereinafter describec. These prisms are shown on theinterior sur- F! OULD RE! "0 L- No. 237,156. Renewed January 16, 1929.

faces of these members, and this cesirabl from the point of view ofhaving a 1 with a smooth exterior, for purposes of r dom from dirt anddust and feasibilit of cleansing when in operation or when ta C, D, E,F, G and paths from the various parts of the luminair U11 i The typicalray A from the sour cident on the upper part of reflector prisms of 3 atthe point of incidence b so constructed as to permit ray A to bedistributed in direction A as desired in upper llGD'liSPllGi'G. Slightlybelow point It is point B on the outer un and the rays at this pointlikewise pass d unit the

in direction B "for d ailoll upper hemisphere. Toward the the. unit thecup begins 1 as to intercept the \Vithin points 5 a on its outer surface1 and refract them in generally "nor rections to the 'er surface on theinterior retlcetr ceive such rays the outer reflector downwarddirection.) 1: plate a, and the light cine luminous di C I ashereinafter described.

That portion of the cup 2 between p' 6 and 9 may most e;..ciently besuppl with external reflecting is which sp the light into two parts. Aportion of this light. represented by typical rays E and F is flectedupward and strikes the reflectin prisms of at such angles as to be transmitted. Typical light ray E tends to brighten up the ceiling andeliminate the possibility of a shadow directly above the unit. Typicallight ray F forms a partof the light in the upper hemisphere which isspread out over the ceiling at a wide angle. The other portion of thelight which strikes cup 2 between 6 and 9 is reflected directly downwardand strikes diffusing bowl Such a typical light ray is G which finallyemerges from 4: as G.

That portion of the light from the light source which strikes therefractor cup 2 between points 9 and 10 (such as ray H) is concentratedby the prisms of the cup into a generally vertical downward direction.

The result is that the bowl 4 receives light 'over its entire surface ina generally clownward direction. This bowl may redistribute the light asdesired but a preferred construction is to use prisms of such acharacter that the light is distributed into the desired directions inthe 060 zone, from each small portion of the bowl so that the desireddistribution or shape of photometric curve is obtained from everysection of the bowl. This will insure that the bowl when viewed frombelow will approximate an appearance of equal luminosity and theintrinsic brilliancy will generally tend toward the least possible valuefor a given size of bowl and emitted candle power.

The light rays C, D, G and H, striking the bowl. 4, should each beconsidered as a pencil of light rays rather than a single light ray,because the distribution of the light as indicated by C, D, G and H whenemerging from 4 is not obtained from a single point on 4 but from a verysmall area, the size of this area depending upon the size of theprismatic patterns or other diffusing means used on 4.

I have previously devised a prismatic construction which is peculiarlyadapted to carry out this feature of the unit. This construction isdescribed in patent application No. 77,500, filed December 24, 1925. Itconsists of a series of parallel prisms running across the bowlseparated by small blank spaces; intersecting this series is anotherseries running in another direction at some predetermined angle with thefirst series; intersecting both of these would be a third series runningat still another angle and possibly a fourth or as many as may bedesired to get-the effect. The cross section of each prism of eachseries is designed to give in one plane the desired distribution oflight. The resulting effect is that each small portion of the bowl hasrunning across it many prisms at different angles each one distributingthe light correctly in a given vertical plane. The distributions meshtogether in such a way that when viewed at a short dis tance the entirebowl appears to be equally luminous. because each small portion of thebowl gives the desired distribution of light.

The reflect ng portion of 3 shown in the drawing as a prismaticreflector smooth onits outer surface with prisms on its inner surface isso designed as to insure total reflection from the outer surface whenthe light is incident as indicated. This is not a necessaryconstruction. Other types of reflectors could be used to accomplish thedesired reflection. Nor is it always necessary that part 2 concentratethe light into a generally horizontal direction. In the figure we haveshown some spread of this light. Cup 2 is used to cooperate with thereflecting portion of 3 in such a way that the desired downwardreflection of light is obtained. The generally cylindrical portion of 2is intended partially to concentrate the light into directions such thatthe reflecting portion of 3 can handle it most effectively. Anymodification of the prisms of 2 with corresponding modifications of thereflecting portion of 3 so that they still cooperate in performing thefunction described is considered as coming within the scope of thisinvention.

The luminair herein described is especially useful for interiors inwhich any close work is performed, or indeed for almost any interior,because the portion of the luminair which gives the direct light appearsilluminated evenly when viewed from any angle, even as low an angle asthe nadir. When a luminair appears equally luminous the intrinsicbrilliancy is at the lowest possible value for the candle powerdelivered, since the entire surface is contributing equally to thiscandle power and intrinsic brilliancy is light intensity divided by thearea from which the intensity is obtained (frequently expressed ascandle power per square inch). While no one, under ordinary conditions,ever views the lower part of the unit-directly at such low angles as thenadir or at 30 or even at higher angles, nevertheless when working onpolished surfaces, such as desks, sized papers, etc., the image of theunit is likely to be reflected from the working surface and thus reachesthe eye from such low angles. When that portion'of the unit contributingto this downward light is equally luminous over its entire surface, thebrilliancy of such reflected images is at a minimum and conditions forclose work are better than would otherwise be obtained.

The typical luminair of this character as shown in the figure is notintended to represent the only possible construction and arrangement ofparts within the scope of this invention, but is intended to show apreferred construction for this class of luminaires.

I claim:

1. A luminair comprising a light source, a lens element surrounding thesource and reducing the divergence of the light in vertical planes, aglobe consisting of a reflector and a bottom plate surrounding the lenselement and source, the reflector being adapted to reflect the light anddeliver it in approximately parallel rays to the bottom plate fortransmission thereby. V

2. A luminair comprising a light source, a lens element surrounding thesource and reducing the divergence of the light in vertical planes, aglobe consisting of a reflector and a diffusing bottom plate surroundingthe cylindrical member and source, the reflector being adapted toreflect the light and deliver it in approximately parallel rays to thebottom plate for distribution thereby.

A luminair comprising a light source, a lens element surrounding thesource and reducing the divergence of the light in vertical planes, aglobe consisting of a reflector and a. prismatic bottom platesurrounding the lens member and source, the reflector being adapted toreflectthe light and deliver it in approximately parallel rays to thebottom plate to obtain substantially the same light distribution fromevery part of the plate.

4. A luminair comprising a light source, a lens element surrounding thesource and reducing the divergence of the light in vertical planes, aglobe consisting of a prismatic glass reflector and a diffusing bottomplate surrounding the cylindrical member and source, the reflectorhaving an upper light transmitting section and a lower reflectingsection adapted to concentrate the light rays received from the innermember in avertical direction to the bottom plate for distribu tion anddirection thereby.

5. A luminair comprising a light source, a cylindrical lens elementsurrounding the source and reducing the divergence of the light invertical planes, a. globe surrounding the cylindrical member and sourceconsisting of a reflector and diffusing bottom plate each provided withprisms on their interior surfaces, the reflector having an upper sectionprovided on its interior with light transmitting prisms and a lowersection provided with interior light reflecting prisms adapted toconcentrate the light rays received from the inner member in a verticaldirection to the interior prisms of the bottom plate for distributionand direction thereby.

6. A luminair comprising a light source, a cylindrical lenticular cupsurrounding the source and a globe surrounding the source and the cup,the lenticular corrugations on the side Walls of' the cup reducing thedivergence of the light in vertical planes, and those on the basethereof in vertical direction, the globe consisting of a reflector anddiffusing bottom plate each provided with prisms on their interiorsurfaces, the reflector having an upper section provided on its interiorwith light transmitting prisms and a lower section provided withinterior light reflecting prisms adapted to concentrate the light raysreceived from the inner member in a vertical direction to the interiorprisms of the bottom plate for distribution and direction thereby.

7. A luminair comprising a light source, a cylindrical cup surroundingthe source and provided with prisms on its exterior surface and a globesurrounding the source and the cup, the corrugations on the side wallsof the cup reducing the divergence of the light in vertical planes andthose on the base thereof in vertical directions, the globe con sistingof a reflector and diffusing bottom plate each provided with prisms ontheir interior surfaces, the reflector having an upper section providedon its interior with light transmitting prisms and a lower sectionprovided with interior light reflecting prisms adapted to concentratethe light rays received from the inner member in a vertical direction tothe interior prisms of the bottom plate for distribution and directionthereby.

Signed at N eWark, in the county of Licking and State of Ohio, this 29day of November, 1927.

THOMAS W. ROLPH.

